Once ignited, violence in the streets is hard to control. People get hurt, lives destroyed.

During the massive protests of the Vietnam War, I sat in the office next to President Nixon. I saw firsthand how explosive emotions can be in this kind of situation. And I know how important it is for a president to strike a temperate but unflinchingly firm posture that assures all that he will maintain law and order.

The protests of the Occupy Wall Street movement started peacefully enough, but now they have begun to turn violent.

Which is why it’s imperative that President Obama speak out. So far, he has been mostly silent, except at the beginning, expressing sympathy for the protestors.

But now this week, the protestors have shut down the Port of Oakland, which endangers the livelihoods of ordinary workers and our exports of agricultural products abroad. Protestors have been smashing bank windows, spray-painting ATMs, and burning garbage. The President must condemn the violence and urge calm.

He must remind the people protesting that this is a nation of laws; that while we must always tolerate peaceful protest, the rights of free speech and freedom of assembly never did, do not, and never will permit violence and the destruction of property and lives.

If he fails to speak in the face of violence, his silence will be taken by many, including the protesters, as a sanction for what they are doing.

Some listeners remember the 60s, the flames that erupted in cities: Detroit, Newark, Los Angeles, the riots that were so wide spread. The words of then Vice-President Hubert Humphrey should be a warning to us all: Referring to the riots, he said that if he had to live in one of our nation’s horrific ghettos, “he might lead a pretty good revolt, too.”

Just the worst thing to say, because he was basically saying to the people who were rioting that it was understandable. What he did was end up fueling the fire.

I know, too, from first-hand experience what kind of pressure you’re under. I remember being in the White House when thousands of angry protestors surrounded us — we couldn’t get out. A flaming canister was tossed at my car when I did get out. The 82nd Airborne, decked out for combat, made quarters in the Executive Office Building across from the White House. The DC Police did a fabulous job through this trying time, showing a massive display of force, but at the same time amazing restraint.

To this day I thank God that the resolve to keep order tempered by prudence kept a lid on things during those volatile periods.

That’s why it is so important for the leader of our nation to speak responsibly and to speak now. If violence spreads like it has in Oakland, who knows where it will lead.

Representative self-government is a fragile balance of freedoms, rights, and order. There can be neither freedom nor enforceable rights in the midst of chaos. Inevitably, any government, any leader, will have to restore order; and the more dire the situation, and the longer they wait, the more force that governments will use to restore order.

Augustine recognized this in his classic work, The City of God. He taught that peace is the tranquility produced by order (tranquillitas ordinis). The first order of government, therefore, is to preserve order, no society can enjoy peace and harmony without it.

So I pray that the President will see the dangerous tipping point that we are reaching, that he will not be silent, he will speak out clearly and without equivocation: We as a free, democratic, and ordered society will not, cannot, tolerate violence in the streets.